全文获取类型
收费全文 | 1433篇 |
免费 | 102篇 |
国内免费 | 3篇 |
出版年
2022年 | 9篇 |
2021年 | 12篇 |
2020年 | 8篇 |
2019年 | 8篇 |
2018年 | 23篇 |
2017年 | 19篇 |
2016年 | 32篇 |
2015年 | 32篇 |
2014年 | 40篇 |
2013年 | 56篇 |
2012年 | 87篇 |
2011年 | 83篇 |
2010年 | 50篇 |
2009年 | 51篇 |
2008年 | 84篇 |
2007年 | 110篇 |
2006年 | 99篇 |
2005年 | 77篇 |
2004年 | 89篇 |
2003年 | 89篇 |
2002年 | 89篇 |
2001年 | 30篇 |
2000年 | 22篇 |
1999年 | 31篇 |
1998年 | 19篇 |
1997年 | 15篇 |
1996年 | 8篇 |
1995年 | 12篇 |
1994年 | 7篇 |
1993年 | 16篇 |
1992年 | 24篇 |
1991年 | 17篇 |
1990年 | 14篇 |
1989年 | 10篇 |
1988年 | 7篇 |
1987年 | 16篇 |
1986年 | 11篇 |
1985年 | 16篇 |
1984年 | 10篇 |
1983年 | 16篇 |
1982年 | 16篇 |
1981年 | 10篇 |
1980年 | 4篇 |
1979年 | 10篇 |
1978年 | 13篇 |
1976年 | 6篇 |
1975年 | 5篇 |
1973年 | 4篇 |
1972年 | 9篇 |
1910年 | 2篇 |
排序方式: 共有1538条查询结果,搜索用时 31 毫秒
41.
Differential Effects of Nitrate and Light on the Expression of Glutamine Synthetases and Ferredoxin-Dependent Glutamate Synthase in Maize 总被引:1,自引:0,他引:1
Sakakibara Hitoshi; Kawabata Shiro; Hase Toshiharu; Sugiyama Tatsuo 《Plant & cell physiology》1992,33(8):1193-1198
The effects of nitrate and light on the expression of genesfor glutamine synthetase (GS) isoproteins and ferredoxin-dependentglutamate synthase (Fd-GOGAT) were studied in different organsof maize seedlings by analyzing the levels of the respectivepolypeptides and mRNAs. In roots, the levels of plastidic GSand of a novel, root-specific GS molecule localized in the extraplastidiccompartment were increased markedly by nitrate, whereas Fd-GOGATand cytosolic GS remained at their initial levels. Ammonia wasnot effective in inducing the plastidic GS and Fd-GOGAT butit did induce the novel GS isoprotein. In leaves, cytosolicand plastidic GSs and Fd-GOGAT were present in both mesophyllcells (MC) and bundle sheath cells (BSC). Upon addition of nitrate,the level of plastidic GS increased preferentially in MC, andupon exposure of etiolated seedlings to light, the levels ofplastidic GS and Fd-GOGAT increased in BSC in a coordinatedmanner. The relationship between the expression of genes forGSs and Fd-GOGAT and the physiological role of the GS/GOGATcycle is discussed in terms of the characteristics of nitrogenmetabolism in roots, MC, and BSC. (Received August 11, 1992; Accepted September 21, 1992) 相似文献
42.
Phenylalanine Ammonia-Lyase Genes from Pisum sativum: Structure, Organ-Specific Expression and Regulation by Fungal Elicitor and Suppressor 总被引:3,自引:0,他引:3
43.
Protochlorophyll(ide) was isolated from dark-grown wild typeand mutant C-2A' cells of Scenedesmus obliquus after dark incubationwith 5-aminolevulinate. Proto-chlorophyll(ide) was detectedin mutant cells grown heterotrophically at 29°C or at 21°C.At the latter temperature chlorophyll synthesis was significant.Regulation of chlorophyll synthesis in algae is discussed.
1Present address: Laboratory of Chemistry, Faculty of Medicine,Teikyo University, Otsuka, Hachioji, Tokyo 192-03, Japan. (Received July 14, 1980; ) 相似文献
44.
The amino acid sequence of a photosynthetic cytochrome c-553 isolated from a brown alga, Petalonia fascia was determined by BrCN fragmentation and a solid phase Edman degradation. The cytochrome contains 85 amino acid residues, giving a molecular weight of 9,803. The complete amino acid sequence is as follows: Val-Asp-Ile-Asn-Asn-Gly-Glu-Ser-Val-Phe-Thr-Ala-Asn-Cys-Ser-Ala-Cys-His-Ala-Gly -Gly-Asn-Asn-Val-Ile-Met-Pro-Glu-Lys-Thr-Leu-Lys-Lys-Asp-Ala-Leu-Glu-Glu-Asn-Gl u-Met-Asn-Asn-Ile-Lys-Ser-Ile-Thr-Tyr-Gln-Val-Thr-Asn-Gly-Lys-Asn-Ala-Met-Pro-A la-Phe-Gly-Gly-Arg-Leu-Ser-Glu-Thr-Asp-Ile-Glu-Asp-Val-Ala-Asn-Phe-Val-Ile-Ser-Gln-Ser-Gln-Lys-Gly-Trp. The highest homology was found between the sequences of cytochromes c-553 of P. fascia and Alaria esculenta, the next between those of P. fascia and Porphyria tenera. 相似文献
45.
The reducing end sugar of an oligosaccharide and 2-aminopyridine were linked by means of reductive amination with sodium cyanoborohydride. The fluorescent derivative of the oligosaccharide thus obtained, which had a positive charge, was subjected to two-dimensional paper electrophoresis. In the first direction, the sugar derivative moved according to its degree of polymerization, and in the second direction, it moved according to the structure of the borate complex. In this way fluorescent derivatives of saccharides were mapped on a sheet of paper. The method was applied to some known mono- and oligosaccharides and to the saccharides obtained by nitrous deamination of the oligosaccharide portions of glycoproteins (fetuin, Take-amylase A, and ovalbumin). The fingerprints thus obtained were characteristic of the chemical structures of the original oligosaccharides. 相似文献
46.
Carbon dioxide enhanced chloroplast regeneration in glucose-bleachedcells of Chlorella protothecoides in the presence of CMU inthe light. Both the formation of chlorophyll and the synthesesof RNA and protein were considerably enhanced. The CO2 metabolism of algal cells during greening was investigatedusing 14C-bicarbonate as the tracer. Radiocarbon was largelyincorporated into purine and pyrimidine bases in nucleic acidand the arginine in protein, specifically at the crabon atomsderived from carbamylphosphate.
1Part of this investigation was reported at the conference onthe "Autonomy and biogenesis of mitochondria and chloroplasts"held at Canberra in 1969 (4). (Received August 19, 1975; ) 相似文献
47.
Chloroplast-nucleus interactions were examined in cells of Euglenagracilis Z synchronized under photoautotrophic conditions. Thechloroplasts were localized near the cell periphery. At an earlystage of the cell cycle, however, some chloroplasts were transientlylocated in the inner space close to the nucleus. Electron microscopyusing serial cell sections revealed that the chloroplast formedprotrusions at several sites, which became associated with thenucleus. The outer membrane of the chloroplast envelope wasin contact, or at least continuous in part, with the outer membraneof the nuclear envelope at the sites of association, and densematerial was present in the chloroplast membrane. A chromosomewas close to each site of the association between these twoorganelles. Most of the chloroplasts including those in associationwith the nucleus were connected by fine bridges. The 4',6-diamidino-2-phenylindole-stainednucleoids in the chloroplast associated with the nucleus appearedto have a thread-like shape. There was another type of chloroplast-nucleusconnection, in which an intervening membranous body was in contactwith the outer part of the nuclear envelope on one side andwith the chloroplast envelope on the other side.
1 This work was reported at the 48th Annual Meeting of the BotanicalSociety of Japan, Kyoto, October, 1983. (Received June 5, 1984; Accepted November 20, 1984) 相似文献
48.
Takashi Nishinaka Yui Yamazaki Atsuko Niwa Hidenori Wake Shuji Mori Tadashi Yoshino 《Biomarkers》2020,25(3):305-313
AbstractBackground: Cerebral small vessel disease (CSVD) is associated with future stroke. Although pathological alteration in small vessels of patients with CSVD can be detected by neuroimaging, diagnosis of CSVD is delayed because it is an asymptomatic disease. The stroke-prone spontaneously hypertensive rat (SHRSP) show similar pathological features to human CSVD and develop stroke-related symptoms with advancing age.Objective: We investigated the time course of haematological parameters in Wistar rats and SHRSP.Material and Methods: Blood cells were analysed using an automated haematological analyser.Results: SHRSP develop stroke-related symptoms including onset of neurological symptoms, decreased body weight and blood brain barrier leakage between 12 and 14?weeks of age. Lymphocyte counts were gradually decreased at 3?weeks before development of stoke-related symptoms and then were further decreased after the development of stroke-related symptoms. The both mean platelet volume and large platelet ratio gradually increased at 3?weeks before the development of stoke-related symptoms. However, although SHRSP showed more microcytic red cells than Wistar rats, the trajectories of change in erythrocyte-related parameters were similar between Wistar rats and SHRSP.Conclusion: Our pilot study suggests that alterations of lymphocyte count and platelet volume predictive indicators for asymptomatic CSVD and symptomatic stroke in SHRSP. 相似文献
49.
Plebejus argyrognomon is an endangered grassland butterfly species in Japan. In this study we focused on the parasitism rate of tachinid flies under different mowing management to obtain knowledge of this possible top-down effect that has been largely ignored. We established three mowing treatments differing in the intensity of mowing, as represented by vegetation height. The results showed that the parasitism rate of P. argyrognomon increased with vegetation height; the parasitism rate in blocks subjected to the highest mowing intensity was 8%, whereas in blocks subjected to the lowest mowing intensity, the rate was 42%. We suggest that clarifying interspecific interactions is important for understanding how habitat management affects grassland-inhabiting butterflies in general. 相似文献
50.